Power injector with ram retraction

ABSTRACT

Various embodiments of syringe plunger driver or ram retraction protocols for a power injector are disclosed. In a first ram retraction protocol ( 184   a ), a first ram may be partially retracted ( 232 ), followed by a full retraction of a second ram ( 234 ), followed by a completion of the retraction of the first ram ( 238 ). In a second ram retraction protocol ( 184   b ), a first ram may be partially retracted ( 252 ), followed by a partial retraction of a second ram ( 254 ), and sometime thereafter each of the first and second rams may be completely retracted ( 260, 262 ). In a third ram retraction protocol ( 184   c ), the first and second rams are simultaneously and partially retracted ( 272 ), and sometime thereafter each of the first and second rams are completely retracted ( 276 ). In a fourth ram retraction protocol ( 184   d ), the first and second rams are simultaneously and fully retracted ( 292 ) based upon a programmed input or the like.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation patent application of U.S.patent application Ser. No. 12/742,934, filed May 14, 2010 (the entiredisclosure being incorporated by reference herein), which is a U.S.National Stage of PCT/US08/84011, filed Nov. 19, 2008, which is anon-provisional patent application of U.S. Provisional PatentApplication Ser. No. 60/989,135, filed on Nov. 20, 2007. Priority isclaimed to each patent application set forth in this Cross-Reference toRelated Applications section.

FIELD OF THE INVENTION

The present invention generally relates to the field of power injectorsand, more particularly, to the manner in which each of its syringedrivers or rams are retracted.

BACKGROUND

Various medical procedures require that one or more fluids be injectedinto the patient. Medical imaging procedures oftentimes involve theinjection of contrast media into the patient, possibly along with salineor other fluids, Other medical procedures involve injecting one or morefluids into a patient for therapeutic purposes. Power injectors may beused for these types of applications.

A power injector generally includes what is commonly referred to as apowerhead. One or more syringes may be mounted to the powerhead invarious manners (e.g., detachably; rear-loading; front-loading;side-loading). Each syringe typically includes what may be characterizedas a syringe plunger, piston, or the like. Each such syringe plunger isappropriately interconnected with an appropriate syringe plunger driverthat is incorporated into the powerhead, such that operation of thesyringe plunger driver axially advances the associated syringe plunger.One typical syringe plunger driver is in the form of a ram that ismounted on a threaded lead or drive screw. Rotation of the drive screwin one rotational direction advances the associated ram in one axialdirection, while rotation of the drive screw in the opposite rotationaldirection advances the associated ram in the opposite axial direction.

Sometimes during contrast-enhanced imaging procedures, a dual-syringepower injector is used. One syringe may contain contrast media (e.g.,iodine or gadolinium solutions) and the other syringe may contain aflushing solution (e.g., saline). In order to increase the likelihoodthat the contents of both syringes have been completely injected, thepower injector may be configured to advance its rams far enough toslightly compress both syringe plungers into the end limits of therespective syringe barrels. If the residual compression force is highenough, it can hinder the manual removal of the syringes by the user,and whether the power injector is of a side load or a front loadconfiguration. When hindered in this manner, users have been known tofirst manually retract both rams individually a slight amount to removethe compression forces, before disconnecting the syringes from the powerinjector.

Dual-syringe power injectors that incorporate an automatic ramretraction feature are also known. In one known configuration, theautomatic ram retraction feature is configured to retract the ramssequentially. In this case, the user must wait for the first ram to becompletely retracted and for the second ram to begin its retractionbefore the compression force has been removed from the both syringes.This wait period can typically be from 10 to 25 seconds. This waitingperiod is considered to be an annoyance by at least some users, asneither of the syringes is typically removed until both rams have beenretracted to at least some degree in accordance with the foregoing.

SUMMARY

First and second aspects of the present invention are each embodied by amethod of operation for a medical fluid delivery system that includes apower injector. This power injector includes a powerhead, first andsecond syringes, and first and second syringe plunger drivers. Thesefirst and second aspects will now be separately addressed.

The first aspect includes executing a programmed retraction sequence,which includes first, second, and third retractions. The firstretraction includes retracting the first syringe plunger driver to afirst intermediate position, where the first syringe plunger driver isthen stopped. The second retraction includes retracting the secondsyringe plunger driver at least toward or in the direction of a secondfully retracted position. The third retraction includes retracting thefirst syringe plunger driver from its first intermediate position to afirst fully retracted position. The first aspect further includesremoving the first and second syringes from the powerhead of the powerinjector.

The second aspect includes executing a programmed retraction sequencethat is automatically initiated by a programmed input to the powerinjector, and that includes first and second retractions. The first andsecond retractions include retracting the first and second syringeplunger drivers, respectively, at least toward or in the direction offirst and second fully retracted positions, respectively. These firstand second retractions occur simultaneously. The second aspect furtherincludes removing the first and second syringes from the powerhead ofthe power injector.

A third aspect of the present invention is embodied by a method ofoperation for a medical fluid delivery system that includes a powerinjector. A user is provided with a first option to enable an automaticinitiation of a syringe plunger driver retraction protocol, as well as asecond option to enable a manual initiation of this same syringe plungerdriver retraction protocol. An injection protocol may be executed usingthe power injector. The syringe plunger driver retraction protocol willbe initiated depending upon the selected option, and will then beexecuted.

The first and second options in accordance with the third aspect may bepresented on one or more graphical user interfaces. Each such graphicaluser interface may be disposed at any appropriate location (e.g., on thepowerhead; on a remote control). The first and second options may beselected in any appropriate manner. Representative ways of making aselection between the first and second options include withoutlimitation by a keyboard, mouse, or touch screen display.

The second and third aspects may be used in combination. In the case ofboth the second aspect and the combination of the second and thirdaspects, the following may be employed individually or incombination: 1) the first syringe may be removed from the powerheadafter the first syringe plunger driver has been at least partiallyretracted, while the second syringe may be removed from the powerheadafter the second syringe plunger driver has been at least partiallyretracted; and 2) the first syringe plunger driver may be retracted toits first fully retracted position without stopping, and the secondsyringe plunger driver may be retracted to its second fully retractedposition without stopping.

The initial retraction of each of the first and second syringe plungerdrivers when utilized by the first, second, and third aspects may beinitiated after the corresponding syringe plunger driver has reached astopped position. This stopped position may correspond with a fullyextended position (e.g., an end of a discharge stroke) or otherwise. Anyretraction of a syringe plunger driver “toward” its corresponding fullyretracted position in the case of each of the first, second, and thirdaspects encompasses stopping at one or more intermediate positions priorto reaching this fully retracted position.

The first and third aspects may also be used in combination. Thefollowing discussion, up to the start of the discussion of the fourthaspect of the present invention, pertains to the first aspect, as wellas to the noted combination of the first and third aspects.

The retraction of the first syringe plunger driver to a firstintermediate position may be done for any appropriate purpose. In oneembodiment, this retraction of the first syringe plunger driver relievesa pressure within the first syringe. The second retraction of the secondsyringe plunger driver (a movement at least toward or in the directionof its second fully retracted position) may be initiated after the firstsyringe plunger driver has reached and been stopped at its firstintermediate position. The retraction of the first syringe plungerdriver to its first intermediate position and the retraction of thesecond syringe plunger driver at least toward or in the direction of itssecond fully retracted position may be initiated simultaneously, mayoccur simultaneously, or both.

The second syringe plunger driver may be retracted to its second fullyretracted position without stopping. The second retraction of the secondsyringe plunger driver at least toward or in the direction of its secondfully retracted position alternatively may entail retracting the secondsyringe plunger driver to a second intermediate position, where thesecond syringe plunger driver is then stopped. The retractions of thefirst and second syringe plunger drivers to their respective first andsecond intermediate positions may occur simultaneously, or sequentiallyand in any order. The first syringe may be removed after the firstsyringe plunger driver has reached its first intermediate position, thesecond syringe may be removed after the second syringe plunger driverhas been at least partially retracted and including after it has reachedits second intermediate position, or both. At least at some point intime after the second syringe plunger driver has been stopped at anysecond intermediate position, the second syringe plunger driver may beretracted to its second fully retracted position.

The first retraction may entail retracting the first syringe plungerdriver a distance that corresponds with a fluid volume of no more thanabout 5 milliliters. Consider the case where the first syringe plungerdriver is retracted from a first stopped position to a firstintermediate position. If the first syringe plunger driver were to beextended from this first intermediate position to this first stoppedposition, the amount of fluid discharged from the first syringe would beno more than about 5 milliliters for the case of the above-notedembodiment. The retraction of the second syringe plunger driver to itssecond intermediate position may entail retracting the second syringeplunger driver a distance that corresponds with a fluid volume of nomore than about 5 milliliters (e.g., between a second stopped positionand a second intermediate position).

The first intermediate position and any second intermediate positioneach may be any appropriate location and each may be established on anyappropriate basis. In one embodiment, the first and/or secondintermediate positions may be at a fixed, constant location from thefirst and second fully retracted position, respectively. In oneembodiment, the first and/or second intermediate positions may be basedupon each of the first stopped position and the first fully retractedposition, and the second stopped position and the second fully retractedposition, respectively. In one embodiment, the location of the firstand/or second intermediate position may be a fixed distance from thefirst and second stopped position, respectively, and regardless of thelocation of the first and second stopped position. For instance, thefirst intermediate position for the first syringe plunger driver may bea distance corresponding with 5 milliliters of fluid from a firststopped position for the first syringe plunger driver, whether the firststopped position is the first fully extended position of the firstsyringe plunger driver for purposes of a fluid delivery protocol, orwhether the first stopped position corresponds with the position of thefirst syringe plunger driver when a fluid delivery protocol has beenprematurely terminated. Similarly, the second intermediate position forthe second syringe plunger driver may be a distance corresponding with 5milliliters of fluid from a second stopped position for the secondsyringe plunger driver, whether the second stopped position is thesecond fully extended position of the second syringe plunger driver forpurposes of a fluid delivery protocol, or whether the second stoppedposition corresponds with the position of the second syringe plungerdriver when a fluid delivery protocol has been prematurely terminated.

The programmed retraction sequence may be initiated on any appropriatebasis. In one embodiment, the programmed retraction sequence isinitiated by a programmed input, by software, or both. In anotherembodiment, the programmed retraction sequence is initiated by userinput.

A fluid delivery protocol (e.g., an injection protocol) may be executedfor purposes of delivering a fluid to a fluid target (e.g., forinjection into a patient). In the case of medical application, thisprotocol may be referred to as a medical fluid delivery protocol. In anycase, this fluid delivery protocol may be in the form of a programmedfluid delivery sequence of one or more programmed parameters. Anyappropriate fluid delivery protocol may be utilized. In one embodiment,the programmed retraction sequence is initiated after the fluid deliveryprotocol has been completed or has been prematurely terminated, andwhich may be determined in any appropriate manner.

Fourth and fifth aspects of the present invention are each embodied by apower injector. This power injector includes a powerhead, first andsecond syringes that are interconnected with the powerhead, first andsecond syringe plunger drivers that are at least interconnectable withthe first and second syringes, respectively, and control logic. Thiscontrol logic is configured to include a syringe plunger driverretraction protocol (hereafter a “retraction protocol”). In the case ofthe fourth aspect, this retraction protocol is configured to retract thefirst syringe plunger driver from a first stopped position to a firstintermediate position that is somewhere between the first stoppedposition and a first fully retracted position, and to also retract thesecond syringe plunger driver from a second stopped position at leasttoward or in the direction of a second fully retracted position. In thecase of the fifth aspect, this retraction protocol is configured toretract the first syringe plunger driver from a first stopped positionat least toward or in the direction of a first fully retracted position,and to simultaneously retract the second syringe plunger driver from asecond stopped position at least toward or in the direction of a secondfully retracted position.

A sixth aspect of the present invention is embodied by a power injector.This power injector includes a powerhead, at least one syringe that isinterconnected with the powerhead (hereafter a “first syringe”), atleast one syringe plunger driver (hereafter a “first syringe plungerdriver”) that is at least interconnectable with its correspondingsyringe, a graphical user interface, and control logic. This controllogic is configured to include a syringe plunger driver retractionprotocol (hereafter a “retraction protocol”), and is further configuredto present first and second options on the graphical user interface. Thefirst option is to enable an automatic initiation of the retractionprotocol. The second option is to enable a manual initiation of theretraction protocol.

The features discussed above with regard to the graphical user interfaceand the selection of the first and second options for the case of thethird aspect may be utilized (individually or in any combination) and/orare equally applicable to the sixth aspect. In one embodiment, theretraction protocol in the case of the sixth aspect may be configured toretract the first syringe plunger driver from a first stopped positionat least toward or in the direction of a first fully retracted position,and to simultaneously retract the second syringe plunger driver from asecond stopped position at least toward or in the direction of a secondfully retracted position. For the case of the above-noted embodiment, aswell as for the case of the fifth aspect of the present invention, theretraction protocol may be configured to retract the first syringeplunger driver from its first stopped position to its first fullyretracted position without stopping, and to simultaneously retract thesecond syringe plunger driver from its second stopped position to itssecond fully retracted position without stopping.

The fourth and sixth aspects may also be used in combination, Unlessotherwise noted, the following discussion pertains to the fourth aspect,as well as to the noted combination of the fourth and sixth aspects.Initially, the discussion presented above with regard to the firstintermediate position for the first syringe plunger driver and anysecond intermediate position for the second syringe plunger driver isequally applicable to both the fourth aspect as well as to thecombination of the fourth and sixth aspects (e.g., a partial retractioncorresponding with a 5 milliliter “limit”).

The retraction protocol may be configured such that the second syringeplunger driver is retracted at least toward or in the direction of itssecond fully retracted position after the first syringe plunger driverhas been retracted from its first stopped position and to its firstintermediate position, where the first syringe plunger driver is thenstopped. The retraction protocol may also be configured such that aninitiation of the retraction of the first syringe plunger driver fromits first stopped position to its first intermediate position, and theinitiation of the retraction of the second syringe plunger driver fromits second stopped position at least toward or in the direction of itssecond fully retracted position, occurs on a simultaneous basis.

The retraction protocol may be configured such that the second syringeplunger driver is retracted from its second stopped position to itssecond fully retracted position without stopping. Alternatively, theretraction protocol may be configured such that the second syringeplunger driver is retracted from its second stopped position to a secondintermediate position, where the second syringe plunger driver is thenstopped. The retraction protocol may be configured such that theretractions of the first and second syringe plunger drivers to theirrespective first and second intermediate positions occur simultaneously,or sequentially, and in any order.

The programmed retraction sequence may be initiated on any appropriatebasis. In one embodiment, the programmed retraction sequence isinitiated by a programmed input, by software, or both, In anotherembodiment, the programmed retraction sequence is initiated by userinput.

A fluid delivery protocol (e.g., an injection protocol) may be executedfor purposes of delivering a fluid to a fluid target (e.g., forinjection into a patient). In the case of medical application, thisprotocol may be referred to as a medical fluid delivery protocol. In anycase, this fluid delivery protocol may be in the form of a programmedfluid delivery sequence of one or more programmed parameters. Anyappropriate fluid delivery protocol may be utilized, In one embodiment,the programmed retraction sequence is initiated after the fluid deliveryprotocol has been completed or has been prematurely terminated.

The remainder of this Summary pertains to each of the first through thesixth aspects. The power injector may be of any appropriate size, shape,configuration, and/or type. The power injector may be used for anyappropriate application where the delivery of one or more fluids isdesired, including without limitation any appropriate medicalapplication (e.g., computed tomography or CT imaging; magnetic resonanceimaging or MRI; SPECT imaging; PET imaging; X-ray imaging; angiographicimaging; optical imaging; ultrasound imaging). The power injector may beused in conjunction with any component or combination of components,such as an appropriate imaging system (e.g., a CT scanner). Forinstance, information could be conveyed between the power injector andone or more other components (e.g., scan delay information, injectionstart signal, injection rate).

Any appropriate number of syringes may be integrated with the powerinjector in any appropriate manner (e.g., detachably; front-loaded;side-loaded; rear-loaded (third aspect only)), any appropriate fluid maybe discharged from a given syringe of the power injector (contrastmedia, a radiopharmaceutical, saline, and any combination thereof), andany appropriate fluid may be discharged from a multiple syringe powerinjector configuration in any appropriate manner (e.g., sequentially,simultaneously), or any combination thereof. In one embodiment, fluiddischarged from a syringe by operation of the power injector is directedinto a conduit, where this conduit is fluidly interconnected with thesyringe in any appropriate manner and directs fluid to a desiredlocation (e.g., to a patient). In one embodiment, each syringe includesa syringe barrel and a plunger that is disposed within and movablerelative to the syringe barrel. This plunger may interface with thepower injector's syringe plunger drive assembly such that the syringeplunger drive assembly is able to advance the plunger in at least onedirection, and possibly in two different, opposite directions.

Any syringe plunger driver that is utilized may be of any appropriatesize, shape, configuration, and/or type. Each such syringe plungerdriver may be capable of at least bi-directional movement (e.g., amovement in a first direction for discharging fluid; a movement in asecond direction for accommodating a loading of fluid or so as return toa position for a subsequent fluid discharge operation). Each suchsyringe plunger driver may interact with its corresponding syringeplunger in any appropriate manner (e.g., by mechanical contact; by anappropriate coupling (mechanical or otherwise)) so as to be able toadvance the syringe plunger in at least one direction (e.g., todischarge fluid). In one embodiment, the syringe plunger driver is inthe form of a ram that is threadably interconnected with a rotatablelead or drive screw. The following characterizations may be made inrelation to each syringe that may be utilized, and thesecharacterizations apply both individually or in any combination: 1) eachsyringe may be of any appropriate size, shape, configuration, size,and/or type; 2) each syringe may be interconnected with the powerhead inany appropriate manner; and 3) each syringe may interface with a syringeplunger driver in any appropriate manner.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic of one embodiment of a power injector.

FIG. 2A is a perspective view of one embodiment of a portablestand-mounted, dual-head power injector.

FIG. 2B is an enlarged, partially exploded, perspective view of apowerhead used by the power injector of FIG. 2A.

FIG. 2C is a schematic of one embodiment of a syringe plunger driveassembly used by the power injector of FIG. 2A.

FIG. 3 is a perspective view of another embodiment of a portable,stand-mounted, dual-head power injector.

FIG. 4 is a schematic of one embodiment of a power injector controlsystem.

FIG. 5 is one embodiment of a power injector control protocol that maybe used by the power injector control system of FIG. 4.

FIG. 6 is another embodiment of a power injector control protocol thatmay be used by the power injector control system of FIG. 4.

FIG. 7 is one embodiment of a ram retraction protocol that may be usedby the power injector control system of FIG. 4, where one of the rams isonly initially partially retracted.

FIG. 8 is one embodiment of a ram retraction protocol that may be usedby the power injector control system of FIG. 4, where both rams are onlyinitially partially retracted and on a sequential basis.

FIG. 9 is one embodiment of a ram retraction protocol that may be usedby the power injector control system of FIG. 4, where both of the ramsare only initially partially retracted and on a simultaneous basis.

FIG. 10 is one embodiment of a ram retraction protocol that may be usedby the power injector control system of FIG. 4, where both of the ramsare simultaneously retracted to a fully retracted position.

DETAILED DESCRIPTION

FIG. 1 presents a schematic of one embodiment of a power injector 10having a powerhead 12. One or more graphical user interfaces or GUIs 11may be associated with the powerhead 12. Each GUI 11: 1) may be of anyappropriate size, shape, configuration, and/or type; 2) may beoperatively interconnected with the powerhead 12 in any appropriatemanner; 3) may be disposed at any appropriate location; 4) may beconfigured to provide one or any combination of the following functions:controlling one or more aspects of the operation of the power injector10; inputting/editing one or more parameters associated with theoperation of the power injector 10; and displaying appropriateinformation (e.g., associated with the operation of the power injector10); or 5) any combination of the foregoing. Any appropriate number ofGUIs 11 may be utilized. In one embodiment, the power injector 10includes a GUI 11 that is incorporated by a console that is separatefrom but which communicates with the powerhead 12. In anotherembodiment, the power injector 10 includes a GUI 11 that is part of thepowerhead 12. In yet another embodiment, the power injector 10 utilizesone GUI 11 on a separate console that communicates with the powerhead12, and also utilizes another GUI 11 that is on the powerhead 12. EachGUI 11 could provide the same functionality or set of functionalities,or the GUIs 11 may differ in at least some respect in relation to theirrespective functionalities.

A syringe 28 may be installed on this powerhead 12 and may be consideredto be part of the power injector 10. Some injection procedures mayresult in a relatively high pressure being generated within the syringe28. In this regard, it may be desirable to dispose the syringe 28 withina pressure jacket 26. The pressure jacket 26 is typically installed onthe powerhead 12, followed by disposing the syringe 25 within thepressure jacket 26. The same pressure jacket 26 will typically remaininstalled on the powerhead 12, as various syringes 28 are positionedwithin and removed from the pressure jacket 26 for multiple injectionprocedures. The power injector 10 may eliminate the pressure jacket 26if the power injector 10 is configured/utilized for low-pressureinjections. In any case, fluid discharged from the syringe 28 may bedirected into a conduit 38 of any appropriate size, shape,configuration, and/or type, which may be fluidly interconnected with thesyringe 28 in any appropriate manner, and which may direct fluid to anyappropriate location (e.g., to a patient).

The powerhead 12 includes a syringe plunger drive assembly 14 thatinteracts (e.g., interfaces) with the syringe 28 to discharge fluid fromthe syringe 28. This syringe plunger drive assembly 14 includes a drivesource 16 (e.g., a motor of any appropriate size, shape, configuration,and/or type, optional gearing, and the like) that powers a drive output18 (e.g., a rotatable drive screw). A ram 20 may be advanced along anappropriate path (e.g., axial) by the drive output 18. The ram 20 mayinclude a coupler 22 for interacting or interfacing with a correspondingportion of the syringe 28 in a manner that will be discussed below.

The syringe 28 includes a plunger or piston 32 that is movably disposedwithin a syringe barrel 30 (e.g., for axial reciprocation along an axiscoinciding with the double-headed arrow B). The plunger 32 may include acoupler 34. This syringe plunger coupler 34 may interact or interfacewith the ram coupler 22 to allow the syringe plunger drive assembly 14to retract the syringe plunger 32 within the syringe barrel 30. Thesyringe plunger coupler 34 may be in the form of a shaft 36 a thatextends from a body of the syringe plunger 32, together with a head orbutton 36 b. However, the syringe plunger coupler 34 may be of anyappropriate size, shape, configuration, and/or type.

Generally, the syringe plunger drive assembly 14 may interact with eachsyringe plunger 32 of the power injector 10 in any appropriate manner(e.g., by mechanical contact; by an appropriate coupling (mechanical orotherwise)) so as to be able to move or advance the syringe plunger 32in at least one direction (e.g., to discharge fluid from thecorresponding syringe 28). That is, although the syringe plunger driveassembly 14 may be capable of bi-directional motion (e.g., via operationof the same drive source 16), the power injector 10 may be configuredsuch that the operation of the syringe plunger drive assembly 14actually only moves each syringe plunger 32 being used by the powerinjector 10 in only one direction. However, the syringe plunger driveassembly 14 may be configured to interact with each syringe plunger 32being used by the power injector 10 so as to be able to move each suchsyringe plunger 32 in each of two different directions (e.g. indifferent directions along a common axial path).

Retraction of the syringe plunger 32 may be utilized to accommodate aloading of fluid into the syringe barrel 30 for a subsequent injectionor discharge, may be utilized to actually draw fluid into the syringebarrel 30 for a subsequent injection or discharge, or for any otherappropriate purpose. Certain configurations may not require that thesyringe plunger drive assembly 14 be able to retract the syringe plunger32, in which case the ram coupler 22 and syringe plunger coupler 34 maynot be required. In this case, the syringe plunger drive assembly 14 maybe retracted for purposes of executing another fluid delivery operation(e.g., after another pre-filled syringe 28 has been installed). Evenwhen a ram coupler 22 and syringe plunger coupler 34 are utilized, itmay such that these components may or may not be coupled when the ram 20advances the syringe plunger 32 to discharge fluid from the syringe 28(e.g., the ram 20 may simply “push on” the syringe plunger coupler 34 oron a proximal end of the syringe plunger 32). Any single motion orcombination of motions in any appropriate dimension or combination ofdimensions may be utilized to dispose the ram coupler 22 and syringeplunger coupler 34 in a coupled state or condition, to dispose the ramcoupler 22 and syringe plunger coupler 34 in an un-coupled state orcondition, or both.

The syringe 28 may be installed on the powerhead 12 in any appropriatemanner. For instance, the syringe 28 could be configured to be installeddirectly on the powerhead 12. In the illustrated embodiment, a housing24 is appropriately mounted on the powerhead 12 to provide an interfacebetween the syringe 28 and the powerhead 12. This housing 24 may be inthe form of an adapter to which one or more configurations of syringes28 may be installed, and where at least one configuration for a syringe28 could be installed directly on the powerhead 12 without using anysuch adapter. The housing 24 may also be in the form of a faceplate towhich one or more configurations of syringes 28 may be installed. Inthis case, it may be such that a faceplate is required to install asyringe 28 on the powerhead 12—the syringe 28 could not be installed onthe powerhead 12 without the faceplate. When a pressure jacket 26 isbeing used, it may be installed on the powerhead 12 in the variousmanners discussed herein in relation to the syringe 28, and the syringe28 will then thereafter be installed in the pressure jacket 26.

The housing 24 may be mounted on and remain in a fixed position relativeto the powerhead 12 when installing a syringe 28. Another option is tomovably interconnect the housing 24 and the powerhead 12 to accommodateinstalling a syringe 28. For instance, the housing 24 may move within aplane that contains the double-headed arrow A to provide one or more ofcoupled state or condition and an un-coupled state or condition betweenthe ram coupler 22 and the syringe plunger coupler 34.

One particular power injector configuration is illustrated in FIG. 2A,is identified by a reference numeral 40, and is at least generally inaccordance with the power injector 10 of FIG. 1, The power injector 40includes a powerhead 50 that is mounted on a portable stand 48, A pairof syringes 86 a, 86 b for the power injector 40 is mounted on thepowerhead 50. Fluid may be discharged from the syringes 86 a, 86 bduring operation of the power injector 40.

The portable stand 48 may be of any appropriate size, shape,configuration, and/or type. Wheels, rollers, casters, or the like may beutilized to make the stand 48 portable. The powerhead 50 could bemaintained in a fixed position relative to the portable stand 48.However, it may be desirable to allow the position of the powerhead 50to be adjustable relative to the portable stand 48 in at least somemanner. For instance, it may be desirable to have the powerhead 50 inone position relative to the portable stand 48 when loading fluid intoone or more of the syringes 86 a, 86 b, and to have the powerhead 50 ina different position relative to the portable stand 48 for performanceof an injection procedure. In this regard, the powerhead 50 may bemovably interconnected with the portable stand 48 in any appropriatemanner (e.g., such that the powerhead 50 may be pivoted through at leasta certain range of motion, and thereafter maintained in the desiredposition).

It should be appreciated that the powerhead 50 could be supported in anyappropriate manner for providing fluid. For instance, instead of beingmounted on a portable structure, the powerhead 50 could beinterconnected with a support assembly, that in turn is mounted to anappropriate structure (e.g., ceiling, wall, floor). Any support assemblyfor the powerhead 50 may be positionally adjustable in at least somerespect (e.g., by having one or more support sections that may berepositioned relative to one more other support sections), or may bemaintained in a fixed position. Moreover, the powerhead 50 may beintegrated with any such support assembly so as to either be maintainedin a fixed position or so as to be adjustable relative the supportassembly.

The powerhead 50 includes a graphical user interface or GUI 52. This GUI52 may be configured to provide one or any combination of the followingfunctions: controlling one or more aspects of the operation of the powerinjector 40; inputting/editing one or more parameters associated withthe operation of the power injector 40; and displaying appropriateinformation (e.g., associated with the operation of the power injector40). The power injector 40 may also include a console 42 and powerpack46 that each may be in communication with the powerhead 50 in anyappropriate manner (e.g., via one or more cables), that may be placed ona table or mounted on an electronics rack in an examination room or atany other appropriate location, or both. The powerpack 46 may includeone or more of the following and in any appropriate combination: a powersupply for the injector 40; interface circuitry for providingcommunication between the console 42 and powerhead 50; circuitry forpermitting connection of the power injector 40 to remote units such asremote consoles, remote hand or foot control switches, or other originalequipment manufacturer (OEM) remote control connections (e.g., to allowfor the operation of power injector 40 to be synchronized with the x-rayexposure of an imaging system); and any other appropriate componentry.The console 42 may include a touch screen display 44, which in turn mayprovide one or more of the following functions and in any appropriatecombination: allowing an operator to remotely control one or moreaspects of the operation of the power injector 40; allowing an operatorto enter/edit one or more parameters associated with the operation ofthe power injector 40; allowing an operator to specify and storeprograms for automated operation of the power injector 40 (which canlater be automatically executed by the power injector 40 upon initiationby the operator); and displaying any appropriate information relation tothe power injector 40 and including any aspect of its operation.

Various details regarding the integration of the syringes 86 a, 86 bwith the powerhead 50 are presented in FIG. 2B. Each of the syringes 86a, 86 b includes the same general components. The syringe 86 a includesplunger or piston 90 a that is movably disposed within a syringe barrel88 a. Movement of the plunger 90 a along an axis 100 a (FIG. 2A) viaoperation of the powerhead 50 will discharge fluid from within thesyringe barrel 88 a through a nozzle 89 a of the syringe 86 a. Anappropriate conduit (not shown) will typically be fluidly interconnectedwith the nozzle 89 a in any appropriate manner to direct fluid to adesired location (e.g., a patient). Similarly, the syringe 86 b includesplunger or piston 90 b that is movably disposed within a syringe barrel68 b. Movement of the plunger 90 b along an axis 100 b (FIG. 2A) viaoperation of the powerhead 50 will discharge fluid from within thesyringe barrel 88 b through a nozzle 89 b of the syringe 86 b. Anappropriate conduit (not shown) will typically be fluidly interconnectedwith the nozzle 89 b in any appropriate manner to direct fluid to adesired location (e.g., a patient).

The syringe 86 a is interconnected with the powerhead 50 via anintermediate faceplate 102 a. This faceplate 102 a includes a cradle 104that supports at least part of the syringe barrel 88 a, and which mayprovide/accommodate any additional functionality or combination offunctionalities. A mounting 82 a is disposed on and is fixed relative tothe powerhead 50 for interfacing with the faceplate 102 a. A ram coupler76 of a ram 74, which are each part of a syringe plunger drive assembly56 for the syringe 86 a, is positioned in proximity to the faceplate 102a when mounted on the powerhead 50. Details regarding the syringeplunger drive assembly 56 will be discussed in more detail below inrelation to FIG. 2C. Generally, the ram coupler 76 may be coupled withthe syringe plunger 90 a of the syringe 86 a, and the ram coupler 76 andram 74 may then be moved relative to the powerhead 50 to move thesyringe plunger 90 a along the axis 100 a (FIG. 2A). It may be such thatthe ram coupler 76 is engaged with, but not actually coupled to, thesyringe plunger 90 a when moving the syringe plunger 90 a to dischargefluid through the nozzle 89 a of the syringe 86 a.

The faceplate 102 a may be moved at least generally within a plane thatis orthogonal to the axes 100 a, 100 b (associated with movement of thesyringe plungers 90 a, 90 b, respectively, and illustrated in FIG. 2A),both to mount the faceplate 102 a on and remove the faceplate 102 a fromits mounting 82 a on the powerhead 50. The faceplate 102 a may be usedto couple the syringe plunger 90 a with its corresponding ram coupler 76on the powerhead 50. In this regard, the faceplate 102 a includes a pairof handles 106 a. Generally and with the syringe 86 a being initiallypositioned within the faceplate 102 a, the handles 106 a may be moved toin turn move/translate the syringe 86 a at least generally within aplane that is orthogonal to the axes 100 a, 100 b (associated withmovement of the syringe plungers 90 a, 90 b, respectively, andillustrated in FIG. 2A). Moving the handles 106 a to one positionmoves/translates the syringe 86 a (relative to the faceplate 102 a) inan at least generally downward direction to couple its syringe plunger90 a with its corresponding ram coupler 76. Moving the handles 106 a toanother position moves/translates the syringe 86 a (relative to thefaceplate 102 a) in an at least generally upward direction to uncoupleits syringe plunger 90 a from its corresponding ram coupler 76.

The syringe 86 b is interconnected with the powerhead 50 via anintermediate faceplate 102 b. A mounting 82 b is disposed on and isfixed relative to the powerhead 50 for interfacing with the faceplate102 b. A ram coupler 76 of a ram 74, which are each part of a syringeplunger drive assembly 56 for the syringe 86 b, is positioned inproximity to the faceplate 102 b when mounted to the powerhead 50.Details regarding the syringe plunger drive assembly 56 again will bediscussed in more detail below in relation to FIG. 2C. Generally, theram coupler 76 may be coupled with the syringe plunger 90 b of thesyringe 86 b, and the ram coupler 76 and ram 74 may be moved relative tothe powerhead 50 to move the syringe plunger 90 b along the axis 100 b(FIG. 2A), It may be such that the ram coupler 76 is engaged with, butnot actually coupled to, the syringe plunger 90 b when moving thesyringe plunger 90 b to discharge fluid through the nozzle 89 b of thesyringe 86 b.

The faceplate 102 b may be moved at least generally within a plane thatis orthogonal to the axes 100 a, 100 b (associated with movement of thesyringe plungers 90 a, 90 b, respectively, and illustrated in FIG. 2A),both to mount the faceplate 102 b on and remove the faceplate 102 b fromits mounting 82 b on the powerhead 50. The faceplate 102 b also may beused to couple the syringe plunger 90 b with its corresponding ramcoupler 76 on the powerhead 50. In this regard, the faceplate 102 b mayinclude a handle 106 b. Generally and with the syringe 86 b beinginitially positioned within the faceplate 102 b, the syringe 86 b may berotated along its long axis 100 b (FIG. 2A) and relative to thefaceplate 102 b. This rotation may be realized by moving the handle 106b, by grasping and turning the syringe 86 b, or both. In any case, thisrotation moves/translates both the syringe 86 b and the faceplate 102 bat least generally within a plane that is orthogonal to the axes 100 a,100 b (associated with movement of the syringe plungers 90 a, 90 b,respectively, and illustrated in FIG. 2A). Rotating the syringe 86 b inone direction moves/translates the syringe 86 b and faceplate 102 b inan at least generally downward direction to couple the syringe plunger90 b with its corresponding ram coupler 76. Rotating the syringe 86 b inthe opposite direction moves/translates the syringe 86 b and faceplate102 b in an at least generally upward direction to uncouple its syringeplunger 90 b from its corresponding ram coupler 76.

As illustrated in FIG. 2B, the syringe plunger 90 b includes a plungerbody 92 and a syringe plunger coupler 94, This syringe plunger coupler94 includes a shaft 98 that extends from the plunger body 92, along witha head 96 that is spaced from the plunger body 92. Each of the ramcouplers 76 includes a larger slot that is positioned behind a smallerslot on the face of the ram coupler 76. The head 96 of the syringeplunger coupler 94 may be positioned within the larger slot of the ramcoupler 76, and the shaft 98 of the syringe plunger coupler 94 mayextend through the smaller slot on the face of the ram coupler 76 whenthe syringe plunger 90 b and its corresponding ram coupler 76 are in acoupled state or condition. The syringe plunger 90 a may include asimilar syringe plunger coupler 94 for interfacing with itscorresponding ram coupler 76.

The powerhead 50 is utilized to discharge fluid from the syringes 86 a,86 b in the case of the power injector 40. That is, the powerhead 50provides the motive force to discharge fluid from each of the syringes86 a, 86 b. One embodiment of what may be characterized as a syringeplunger drive assembly is illustrated in FIG. 2C, is identified byreference numeral 56, and may be utilized by the powerhead 50 todischarge fluid from each of the syringes 86 a, 86 b. A separate syringeplunger drive assembly 56 may be incorporated into the powerhead 50 foreach of the syringes 86 a, 86 b. In this regard and referring back toFIGS. 2A-B, the powerhead 50 may include hand-operated knobs 80 a and 80b for use in separately controlling each of the syringe plunger driveassemblies 56.

Initially and in relation to the syringe plunger drive assembly 56 ofFIG. 2C, each of its individual components may be of any appropriatesize, shape, configuration and/or type. The syringe plunger driveassembly 56 includes a motor 58, which has an output shaft 60. A drivegear 62 is mounted on and rotates with the output shaft 60 of the motor58. The drive gear 62 is engaged or is at least engageable with a drivengear 64. This driven gear 64 is mounted on and rotates with a drivescrew or shaft 66, The axis about which the drive screw 66 rotates isidentified by reference numeral 68. One or more bearings 72appropriately support the drive screw 66.

A carriage or ram 74 is movably mounted on the drive screw 66.Generally, rotation of the drive screw 66 in one direction axiallyadvances the ram 74 along the drive screw 66 (and thereby along axis 68)in the direction of the corresponding syringe 86 a/b, while rotation ofthe drive screw 66 in the opposite direction axially advances the ram 74along the drive screw 66 (and thereby along axis 68) away from thecorresponding syringe 86 a/b. In this regard, the perimeter of at leastpart of the drive screw 66 includes helical threads 70 that interfacewith at least part of the ram 74. The ram 74 is also movably mountedwithin an appropriate bushing 78 that does not allow the ram 74 torotate during a rotation of the drive screw 66. Therefore, the rotationof the drive screw 66 provides far an axial movement of the ram 74 in adirection determined by the rotational direction of the drive screw 66.

The ram 74 includes a coupler 76 that that may be detachably coupledwith a syringe plunger coupler 94 of the syringe plunger 90 a/b of thecorresponding syringe 86 a/b. When the ram coupler 76 and syringeplunger coupler 94 are appropriately coupled, the syringe plunger 90 a/bmoves along with ram 74. FIG. 2C illustrates a configuration where thesyringe 86 a/b may be moved along its corresponding axis 100 a/b withoutbeing coupled to the ram 74. When the syringe 86 a/b is moved along itscorresponding axis 100 a/b such that the head 96 of its syringe plunger90 a/b is aligned with the ram coupler 76, but with the axes 68 still inthe offset configuration of FIG. 2C, the syringe 86 a/b may betranslated within a plane that is orthogonal to the axis 68 along whichthe ram 74 moves. This establishes a coupled engagement between the ramcoupler 76 and the syringe plunger coupler 96 in the above-noted manner.

FIG. 3 is a perspective view of one embodiment of a power injector 110that includes a support or stand 112, along with a powerhead 122 that ismovably interconnected with the support 112 by a movable joint 120(e.g., pivotally, for instance to accommodate the powerhead 122 being inone position to draw or otherwise load a fluid into one or more syringes150, and to further accommodate the powerhead 122 being in anotherposition for an injection procedure). The support 112 may be of anyappropriate size, shape, configuration, and/or type. The support 112 ofthe illustrated embodiment is in the form of a movable or portable base114 (e.g., having a plurality of casters, rollers, or the like forportability), along with a column 118 that extends at least generallyupwardly from the base 114. It should be appreciated that the support112 need not include transportability functionality in all instances.Other configurations may be appropriate for the support 112. Forinstance, the support 112 could be adapted so as to be mountable to anappropriate structure (e.g., a wall, ceiling, or floor), could beadapted so as to include one or more positional adjustability features,or both.

The powerhead 122 may include an appropriate display or user interfacescreen 146 to accommodate providing one or more operational inputs tothe power injector 110, to display various information, or the like. Oneor more other data input devices of any appropriate type could beintegrated with the powerhead 122 outside of the display 146 as well(e.g., a remote console). The powerhead 122 is of a dual-headconfiguration, and thereby incorporates a pair of what may becharacterized as syringe drivers 126 a, 126 b. Further in this regard,the power injector 110 includes a syringe 150 for each of the syringedrivers 126 a, 126 b, where each syringe includes a plunger 158 that maybe axially advanced to discharge fluid. Typically, these syringes 150will be detachably interconnected with (e.g., mounted on) the powerhead122 in any appropriate manner, although such need not always be thecase. In the illustrated embodiment, the syringes 150 are “side loaded”by disposing each syringe 150 within an appropriately sized concaveopening in the powerhead 122. As such, the power injector 110 may alsobe characterized as being of a side-loading type.

Each syringe 150 may be of any appropriate size, shape, configuration,and/or type. Although the syringes 150 discharge into common tubing inthe illustrated embodiment, such need not always be the case. The powerinjector 110 may integrate the powerhead 122 and syringes 150 in anyappropriate manner, including without limitation using pressure jacketsor without using pressure jackets. The powerhead 122 could also beadapted to utilize any appropriate number of syringes 150, includingwithout limitation a single syringe 150 (e.g., a single-headconfiguration).

Each syringe driver 126 a, 126 b includes a ram 130 that is threadablyengaged with a corresponding drive screw (not shown, but containedwithin the powerhead housing). Rotation of a given drive screw axiallyadvances its corresponding ram 130 along its long axis in a directionthat is dictated by the rotational direction of the drive screw. Thedrive screws are rotated through an operative interconnection with amotor 142 of the power injector 110, where the motor 142 may be of anyappropriate size, shape, configuration, and/or type (e.g., an electricmotor, a hydraulic motor, pneumatic motor, a piezoelectric motor).

Axial movement of a given ram 130 in the direction of its correspondingsyringe 150 provides for a fluid discharge from this syringe 150, whilean axial movement of a given ram 130 away from its corresponding syringe150 accommodates, for instance, loading or an introduction of anappropriate fluid into this syringe 150, a removal of the syringe 150,or both. The ram 130 may be coupled with a plunger 158 that is at leastpartially disposed within the syringe 150, such that movement of the ram130 away from its corresponding syringe 150 retracts its associatedplunger 158. In the embodiment of FIG. 3, however, the end of the ram130 merely “butts up” against its corresponding syringe plunger 158.Therefore, advancing a ram 130 toward its corresponding syringe 150 inthe FIG. 3 configuration will cause the ram 130 to engage itscorresponding plunger 158 to advance the same for an injection. However,retracting the ram 130 will cause the same to disengage itscorresponding plunger 158, for instance such that the correspondingsyringe 150 may be removed from the powerhead 122.

The power injectors 10, 40, 110 of FIGS. 1, 2A-C, and 3 each may be usedfor any appropriate application, including without limitation formedical imaging applications where fluid is injected into a subject(e.g., a patient). Representative medical imaging applications for thepower injectors 10, 40, 110 include without limitation computedtomography or CT imaging, magnetic resonance imaging or MRI, SPECTimaging, PET imaging, X-ray imaging, angiographic imaging, opticalimaging, and ultrasound imaging. The power injectors 10, 40, 110 eachcould be used alone or in combination with one or more other components.The power injectors 10, 40, 110 each may be operatively interconnectedwith one or more components, for instance so that information may beconveyed between the power injector 10, 40, 110 and one or more othercomponents (e.g., scan delay information, injection start signal,injection rate).

Any number of syringes may be utilized by each of the power injectors10, 40, 110, including without limitation single-head configurations(for a single syringe) and dual-head configurations (for two syringes).In the case of a multiple syringe configuration, each power injector 10,40, 110 may discharge fluid from the various syringes in any appropriatemanner and according to any timing sequence (e.g., sequential dischargesfrom two or more syringes, simultaneous discharges from two or moresyringes, or any combination thereof). Each such syringe utilized byeach of the power injectors 10, 40, 110 may include any appropriatefluid, for instance contrast media, a radiopharmaceutical, saline, andany combination thereof. Each such syringe utilized by each of the powerinjectors 10, 40, 110 may be installed in any appropriate manner (e.g.,rear-loading configurations may be utilized; front-loadingconfigurations may be utilized; side-loading configurations may beutilized).

FIG. 4 illustrates one embodiment of a power injector control system 170that may be utilized by any appropriate power injector, includingwithout limitation the power injector 10 of FIG. 1, the power injector40 of FIGS. 2A-C, and the power injector 110 of FIG. 3. The powerinjector control system 170 may include one or more data entry devices172 of any appropriate configuration and/or type (e.g., a keyboard, amouse, a touch screen display, a soft key display, a touch pad, a trackball). One or more of these data entry devices 172 may be operativelyinterconnected with a power injector control logic or module 174. Thepower injector control module 174 may be of any appropriate form and/orconfiguration, may be implemented or integrated in any appropriatemanner, or both (e.g., in the power injector software; implemented bysoftware, hardware, firmware, and any combination thereof). In oneembodiment, the functionality of the control logic 174 is provided byone or more processors of any appropriate size, shape, configuration,and/or type. In one embodiment, the functionality of the control Logic174 is provided by one or more computers.

The power injector control module 174 may be configured to include atleast one fluid delivery or injection protocol 176 (e.g., for a medicalapplication, and which may be referred to as a medical fluid deliveryprocedure or operation) and a ram retraction protocol 184, and each ofwhich may be in the form of a programmed sequence. For a medicalapplication, the protocol 176 may be referred to as a medical fluiddelivery protocol 176. Each injection protocol 176 may be configured tocontrol the manner in which one or more fluids are being delivered to afluid target, such as by being injected into a patient. A particularinjection protocol 176 may be configured to deliver a programmed volumeof a first fluid at a programmed flow rate, as well as a programmedvolume of a second fluid at a programmed flow rate. Each delivery ofeach of the first and second fluids may be characterized as a phase. Oneor more phases may be utilized for each of the first and second fluids.In one embodiment, the first fluid is contrast media and the secondfluid is saline, The ram retraction protocol 184 will be discussed inmore detail below, but generally is configured to control the manner inwhich each syringe plunger driver (e.g., a ram) is retracted, forinstance after execution or upon completion of an injection protocol176.

The power injector control module 174 of FIG. 4 may include one or moreadditional protocols as desired/required, and each of which may be inthe form of a programmed sequence. Representative protocols that may beutilized by the power injector control module 174 as desired/required,in addition to at least one injection protocol 176 and a ram retractionprotocol 184, include without limitation an OptiBolus® protocol 178, aTiming Bolus® protocol 180, and a drip mode protocol 182. Generally, theOptiBolus® protocol 178 may be configured to deliver an exponentiallydecaying flow rate injection that optimizes the contrast usage andprovides an extended period of uniform enhancement of the area ofinterest. The Timing Bolus® injection protocol 180 may be configured toprovide a timing bolus injection—a small volume of contrast media,followed by a small volume of saline—to a patient for purposes ofdetermining the optimal scan delay needed to capture the contrast mediain the area of interest. The drip mode protocol 182 may be configured toprovide a drip injection —a low flow rate injection of a small volume ofsaline delivered to the patient to keep open the fluid pathway from thepower injector to the patient.

One embodiment of a power injector control protocol 190 is illustratedin FIG. 5, and may be utilized by the power injector control module 174discussed above in relation to FIG. 4 to execute an injection protocol176 and a ram retraction protocol 184. The power injector controlprotocol 190 is illustrated in relation to a dual-head power injector—apower injector having a pair of syringes and a corresponding syringeplunger driver or ram. Hereafter, such a power injector may be referredto as having an A side (e.g., one of the syringes and its correspondingsyringe plunger driver or ram), as well as a B side (e.g., the other ofthe syringes and its corresponding syringe plunger driver or ram). Eachof the A and B sides may contain any appropriate fluid (e.g., contrastmedia, a radiopharmaceutical, saline, and any combination thereof). Itwill be appreciated that the power injector control protocol 190 may beadapted for use with a power injector that utilizes any appropriatenumber of syringes.

The power injector control protocol 190 is configured to allow aninjection protocol 176 to be input in any appropriate manner (e.g., viaone or more data entry devices 172 (FIG. 4) or selected in anyappropriate manner (e.g., via one or more data entry devices 172 (FIG.4), for instance from a plurality of injection protocols 176 stored inmemory and accessible through the power injector control protocol 190).The power injector control protocol 190 is configured to allow the ramretraction protocol 184 to be initiated on two different bases. Anautomatic initiation of the ram retraction protocol 184 may be initiatedthrough execution of step 194 (e.g., via user input using a data entrydevice 172 (FIG. 4)). A manual initiation of the ram retraction protocol184 may be initiated through execution of step 196 (e.g., via user inputusing a data entry device 172 (FIG. 4)). An option to enable anautomatic initiation of the ram retraction protocol (step 194), or toenable a manual initiation of the ram retraction protocol 184 (step194), may be presented to a user on one or more graphical userinterfaces at any appropriate location (e.g., on a powerhead, on aremote control). It should be appreciated that steps 192, 194, and 196may be executed in any appropriate manner and in any appropriatesequence.

Step 198 of the power injector protocol 190 of FIG. 5 is directed toexecuting the injection protocol 176 that was input or selected in step192. The ram retraction protocol 184 is executed by step 200 of thepower injector control protocol 190, and in accordance with step 194 or196 (e.g., whichever option was previously enabled). In one embodiment,the ram retraction protocol 184 is initiated either automatically ormanually only after the injection protocol 176 has been completed orterminated. However, the ram retraction protocol 184 could be initiatedand executed at least in part during a continued execution of theinjection protocol 176 (e.g., if the side A syringe plunger driver orram has reached its fully extended position (e.g., the end of itsdischarge stroke), the ram retraction protocol 184 could be configuredto initiate a retraction of the side A syringe plunger driver or rameven though the side B syringe plunger driver or ram has not yet reachedits fully extended position (e.g., the end of its discharge stroke)pursuant to the injection protocol 176.

The side A and side B syringes may be removed from the powerhead of thepower injector, in accordance with step 202 of the power injectorcontrol protocol 190, at any appropriate time after the injectionprotocol 176 has been completed or terminated. In one embodiment, theside A and side B syringes are removed only after their correspondingsyringe plunger driver or ram has at least been partially retractedthrough execution of the ram retraction protocol 184 (step 200). Theprotocol 190 may return control to any appropriate portion of the powerinjector control module 174 (FIG. 4), for instance through execution ofstep 204.

Another embodiment of a power injector control protocol 210 isillustrated in FIG. 6, and may be utilized by the power injector controlmodule 174 discussed above in relation to FIG. 4 to execute an injectionprotocol 176 and a ram retraction protocol 184. The power injectorcontrol protocol 210 is illustrated in relation to a dual-head powerinjector—a power injector having a pair of syringes and a correspondingsyringe plunger driver or ram. It will be appreciated that the powerinjector control protocol 210 may be adapted for use with a powerinjector that utilizes any appropriate number of syringes.

The power injector control protocol 210 may accommodate the provision ofuser input in any appropriate manner, for any appropriate purpose (e.g.,for inputting/selecting a particular injection protocol 176) and inaccordance with execution of step 212 of the protocol 210. User inputmay not be required in all instances. In any case, an injection protocol176 is executed in accordance with step 214. A ram retraction protocol184 is also executed. How the ram retraction protocol 184 is initiatedis subject to a number of characterizations. One characterization isthat there is a programmed transfer to the ram retraction protocol 184and as reflected by step 216, and the ram retraction protocol 184 isthereafter executed through execution of step 220. Anothercharacterization is that the power injector control protocol 210 may beconfigured to automatically execute the ram retraction protocol 184,versus in direct response to user input. Another characterization isthat the configuration of the power injector control protocol 210 itselfmay transfer control to the ram retraction protocol 184.

The side A and side B syringes may be removed from the powerhead of thepower injector, through execution of step 222 of the power injectorcontrol protocol 210, at any appropriate time after the injectionprotocol 176 has been completed or terminated. In one embodiment, theside A and side B syringes are removed only after their correspondingsyringe plunger driver or ram has at least been partially retractedthrough execution of the ram retraction protocol 184 (step 220). Theprotocol 210 may return control to any appropriate portion of the powerinjector control module 174 (FIG. 4), for instance through execution ofstep 224.

The ram retraction protocol 184 discussed above in relation to the powerinjector control system 170 of FIG. 4, the power injector controlprotocol 190 of FIG. 5, and the power injector control protocol 210 ofFIG. 6, may be of any appropriate configuration. FIGS. 7-10 illustratevarious embodiments of this ram retraction protocol 184, and again whichmay be in the form of a programmed sequence. In one embodiment, each ofthese protocols may be initiated (e.g., automatically or manually) afterthe associated injection protocol 176 has been completed or terminated.However, at least certain of the ram retraction protocols of FIGS. 7-10could be initiated and executed at least in part during a continuedexecution of the injection protocol 176 (e.g., if the side A syringeplunger driver or ram has reached its fully extended position (e.g., theend of its discharge stroke), a particular ram retraction protocol couldbe configured to initiate a retraction of the side A syringe plungerdriver or ram even though the side B syringe plunger driver or ram hasnot yet reached its fully extended position (e.g., the end of itsdischarge stroke) pursuant to the injection protocol 176). The side-loadconfiguration of the power injector 110 of FIG. 3 is particularly suitedfor the ram retraction protocols of FIGS. 7-10. As noted above and inthe case of the power injector 110 of FIG. 3, the retraction of its rams130 does not retract the corresponding syringe plunger 158. Therefore,once the rams 130 have been retracted at least a certain amount and havethereby become disengaged with the corresponding syringe plunger 158,the syringes 150 may be more readily removed.

The ram retraction protocol 184 a of FIG. 7 may be configured to assesswhether the associated fluid delivery or injection protocol has beencompleted or terminated through execution of step 230. However and inaccordance with the foregoing, step 230 may not be required in allinstances. Whether the ram retraction protocol 184 a is automatically ormanually initiated (e.g., in accordance with the power injector controlprotocol 190 of FIG. 5), the ram retraction protocol 184 a retracts theside A syringe plunger driver or ram from a first stopped position(e.g., its fully extended position for purposes of the correspondinginjection protocol) to a first intermediate position that is somewherebetween this first stopped position and a first fully retracted positionfor the side A syringe plunger driver or ram. That is and in accordancewith step 232, the side A syringe plunger driver or ram is partiallyretracted, and it may be partially retracted any appropriateamount/distance. In one embodiment, the partial retraction of the side Asyringe plunger driver or ram corresponds with a fluid volume of no morethan about 5 milliliters. For instance, if the side A syringe plungerdriver or ram was advanced from the first intermediate position to thefirst stopped position, there would be a discharge of no more than about5 milliliters from the first syringe in the case of the above-notedembodiment.

After the side A syringe plunger driver or ram has been partiallyretracted in accordance with step 232 of the ram retraction protocol 184a of FIG. 7, the side B syringe plunger driver or ram is fully retractedor is retracted from a second stopped position (e.g., its fully extendedposition for purposes of the corresponding injection protocol) to asecond fully retracted position. Once the side B syringe plunger driveror ram has reached its second fully retracted position (and which may bedetermined in any appropriate manner for purposes of step 236 of the ramretraction protocol 184 a), step 238 of the protocol 184 a provides fora retraction of the side A syringe plunger driver or ram from its firstintermediate position (associated with step 232) to its first fullyretracted position.

The side A syringe may be removed at any appropriate time and inaccordance with step 240 of the ram retraction protocol 184 a of FIG. 7,and the side B syringe may be removed at any appropriate time and inaccordance with step 242 of the ram retraction protocol 184 a. Thepartial retraction of the side A syringe plunger driver or ramassociated with step 232 may be executed to relieve pressure on the sideA syringe such that it may be removed from the powerhead prior to theside A syringe plunger driver or ram having reached its first fullyretracted position. Therefore, an operator may remove the side A syringepursuant to step 240 any time after execution of step 232. An operatormay remove the side B syringe pursuant to step 242 after the side Bsyringe plunger driver or ram has been retracted at least a certaindistance from its second stopped position and in accordance with step234. The protocol 184 a may return control to any appropriate portion ofthe power injector control module 174 (FIG. 4), for instance throughexecution of step 244.

The configuration of the ram retraction protocol 184 a of FIG. 7 isparticularly suited for power injector configurations that do not allowfor the simultaneous operation of both of its A and B sides, althoughthe ram retraction protocol 184 a may be used with any appropriate powerinjector. Some power injectors use a single motor and a single drivecircuit to separately drive the A and B side syringe plunger drivers orrams. Other power injectors use a pair of motors, but only a singledrive circuit, to separately drive the A and B side syringe plungerdrivers or rams. It should be appreciated that the A and B sides of thepower injector could be reversed for purposes of the ram retractionprotocol 184 a.

The ram retraction protocol 184 b of FIG. 8 may be configured to assesswhether the associated fluid delivery or injection protocol has beencompleted or terminated through execution of step 250. However and inaccordance with the foregoing, step 250 may not be required in allinstances. Whether the ram retraction protocol 184 b is automatically ormanually initiated (e.g., in accordance with the power injector controlprotocol 190 of FIG. 5), the ram retraction protocol 184 b retracts theside A syringe plunger driver or ram from a first stopped position(e.g., its fully extended position for purposes of the correspondinginjection protocol) to a first intermediate position that is somewherebetween this first stopped position and a first fully retracted positionfor the side A syringe plunger driver or ram. That is and in accordancewith step 252, the side A syringe plunger driver or ram is partiallyretracted, and it may be partially retracted any appropriateamount/distance. However and in one embodiment, the partial retractionof the side A syringe plunger driver or ram may correspond with a fluidvolume of no more than about 5 milliliters and in accordance with theforegoing.

The ram retraction protocol 184 b of FIG. 8 retracts the side B syringeplunger driver or ram from a second stopped position (e.g., its fullyextended position for purposes of the corresponding injection protocol)to a second intermediate position that is somewhere between this secondstopped position and a second fully retracted position for the side Bsyringe plunger driver or ram. That is and in accordance with step 254,the side B syringe plunger driver or ram is partially retracted, and itmay be partially retracted any appropriate amount/distance. However andin one embodiment, the partial retraction of the side B syringe plungerdriver or ram may correspond with a fluid volume of no more than about 5milliliters and in accordance with the foregoing. Although the side Aand side B syringe plunger drivers or rams could be retracted the sameamount/distance, such is not required.

The side A syringe may be removed at any appropriate time and inaccordance with step 256 of the ram retraction protocol 184 b of FIG. 8,and the side B syringe may be removed at any appropriate time and inaccordance with step 258 of the ram retraction protocol 184 b. Thepartial retraction of the side A syringe plunger driver or ramassociated with step 252 may be executed to relieve pressure on the sideA syringe such that it may be removed from the powerhead prior to theside A syringe plunger driver or ram having reached its first fullyretracted position. Therefore, an operator may remove the side A syringepursuant to step 256 any time after execution of step 252. Similarly,the partial retraction of the side B syringe plunger driver or ramassociated with step 254 may be executed to relieve pressure on the sideB syringe such that it may be removed from the powerhead prior to theside B syringe plunger driver or ram having reached its second fullyretracted position. Therefore, an operator may remove the side B syringepursuant to step 258 any time after execution of step 254.

Both the A and B side syringe plunger drivers or rams are returned totheir respective fully retracted positions at some point in time afterthe partial retraction associated with steps 252 and 254. The ramretraction protocol 184 b is configured to retract the side A syringeplunger driver or ram from its first intermediate position to its firstfully retracted position (step 260). The ram retraction protocol 184 bis also configured to retract the side B syringe plunger driver or ramfrom its second intermediate position to its second fully retractedposition (step 262). Steps 260 and 262 may be executed in any orderafter each of steps 252 and 254 have been executed. The protocol 184 bmay return control to any appropriate portion of the power injectorcontrol module 174 (FIG. 4), for instance through execution of step 264.

The configuration of the ram retraction protocol 184 b of FIG. 8 isparticularly suited for power injector configurations that do not allowfor the simultaneous operation of both of its A and B sides, althoughthe ram retraction protocol 184 b may be used with any appropriate powerinjector. Some power injectors use a single motor and a single drivecircuit to separately drive the A and B side syringe plunger drivers orrams. Other power injectors use a pair of motors, but only a singledrive circuit, to separately drive the A and B side syringe drivers orrams. In the illustrated embodiment: 1) the A side syringe plungerdriver or ram is retracted (step 252); 2) after the A side syringeplunger driver or ram has reached and stopped at its first intermediateposition, the B side syringe plunger driver or ram is retracted (step254); 3) after the B side syringe plunger driver or ram has reached andstopped at its second intermediate position, the A side syringe plungerdriver or ram is retracted to its first fully retracted position (step260); and 4) after the A side syringe plunger driver or ram has reachedand stopped at its first fully retracted position, the B side syringeplunger driver or ram is retracted to its second fully retractedposition (step 262). It should be appreciated that steps 252 and 254could be executed in any order (e.g., the B side syringe plunger driveror ram could be partially retracted before the A side syringe plungerdriver or ram is partially retracted), and that steps 260 and 262 couldbe executed in any order (e.g., the B side syringe plunger driver or ramcould be retracted from its second intermediate position to its secondfully retracted position before the A side syringe plunger driver or ramis retracted from its first intermediate position to its first fullyretracted position) and regardless of the order in which steps 252 and254 were executed.

The ram retraction protocol 184 c of FIG. 9 may be configured to assesswhether the associated fluid delivery or injection protocol has beencompleted or terminated through execution of step 270. However and inaccordance with the foregoing, step 270 may not be required in allinstances. Whether the ram retraction protocol 184 c is automatically ormanually initiated (e.g., in accordance with the power injector controlprotocol 190 of FIG. 5), the ram retraction protocol 184 c retracts theside A syringe plunger driver or ram from a first stopped position(e.g., its fully extended position for purposes of the correspondinginjection protocol) to a first intermediate position that is somewherebetween this first stopped position and a first fully retracted positionfor the side A syringe plunger driver or ram, and simultaneouslyretracts the side B syringe plunger driver or ram from a second stoppedposition (e.g., its fully extended position for purposes of thecorresponding injection protocol) to a second intermediate position thatis somewhere between this second stopped position and a second fullyretracted position for the side B syringe plunger driver or ram. That isand in accordance with step 272, the side A syringe plunger driver orram and the side B syringe plunger driver or ram are each partiallyretracted and on a simultaneous basis, and each may be partiallyretracted any appropriate amount/distance. However and in oneembodiment, the partial retraction of both the side A side B syringeplunger drivers or rams corresponds with a fluid volume of no more thanabout 5 milliliters and in accordance with the foregoing.

The side A syringe may be removed at any appropriate time and inaccordance with step 274 of the ram retraction protocol 184 c of FIG. 9,and the side B syringe may be removed at any appropriate time and inaccordance with step 276 of the ram retraction protocol 184 c. Thepartial retraction of the side A and B syringe plunger drivers or ramsassociated with step 272 may be executed to relieve pressure on the sideA and B syringes such that they may be removed from the powerhead.Therefore, an operator may remove the side A and B syringes pursuant tostep 274 any time after the execution of step 272.

Both the A and B side syringe plunger drivers or rams are returned totheir respective fully retracted positions at some point in time afterthe partial retraction associated with step 272. In the illustratedembodiment, the ram retraction protocol 184 c is configured to retractthe side A syringe plunger driver or ram from its first intermediateposition to its first fully retracted position and to retract the side Bsyringe plunger driver or ram from its second intermediate position toits second fully retracted position (step 276) after the expiration of apredetermined/programmed amount of time from when the side A and Bsyringe plunger drivers or rams have stopped at their respective firstand second intermediate positions (step 272). The protocol 184 b mayreturn control to any appropriate portion of the power injector controlmodule 174 (FIG. 4), for instance through execution of step 278.

The ram retraction protocol 184 d of FIG. 10 may be configured to assesswhether the associated fluid delivery injection protocol has beencompleted or terminated through execution of step 290. However and inaccordance with the foregoing, step 290 may not be required in allinstances. Whether the ram retraction protocol 184 d is automatically ormanually initiated (e.g., in accordance with the power injector controlprotocol 190 of FIG. 5), a simultaneous retraction of the side A andside B syringe plunger drivers or rams is initiated by step 292. Thatis, the ram retraction protocol 184 d retracts the side A syringeplunger driver or ram from a first stopped position (e.g., its fullyextended position for purposes of the corresponding injection protocol)to a first fully retracted position, and simultaneously retracts theside B syringe plunger driver or ram from a second stopped position(e.g., its fully extended position for purposes of the correspondinginjection protocol) to a second fully retracted position. That is and inaccordance with step 292, the side A syringe plunger driver or ram andthe side B syringe plunger driver or ram are each fully retracted and ona simultaneous basis.

How step 292 of the ram retraction protocol 184 d is initiated issubject to a number of characterizations. One characterization is thatthere is a programmed transfer to step 292. Another characterization isthat the ram retraction protocol 184 d may be configured toautomatically execute step 292 (e.g., a programmed input), versus indirect response to user input. Another characterization is that theconfiguration of the ram retraction protocol 184 d itself may transfercontrol to step 292. Another characterization is that step 292 is partof a programmed sequence. Yet another characterization is that step 292is not initiated in direct response to user/operator input.

The side A and side B syringes may be removed at any appropriate timeafter the simultaneous retraction of the side A and side B syringeplunger drivers or rams has been initiated, and in accordance with step294 of the ram retraction protocol 184 d of FIG. 10. The protocol 184 dmay return control to any appropriate portion of the power injectorcontrol module 174 (FIG. 4), for instance through execution of step 296.

A number of points may be made in relation to each of the ram retractionprotocols 184 a-d of FIGS. 7-10. One is that each of these protocols 184a-d; 1) may be part of the power injector control logic or module 174 ofFIG. 4; 2) may be used in each of the power injector control protocols190, 210 of FIGS. 5 and 6, respectively, and 3) may define a programmedsequence at least in relation to the above-noted steps directed toretracting a syringe plunger driver or ram. The ram retraction protocol184 a of FIG. 7 includes at least steps 232, 234, 236, and 238 as aprogrammed sequence. The ram retraction protocol 184 b of FIG. 8includes at least steps 252, 254, 260, and 262 as a programmed sequence.The ram retraction protocol 184 c of FIG. 9 includes at least steps 272and 276 as a programmed sequence. The ram retraction protocol 184 d ofFIG. 10 includes at least step 292 as a programmed sequence.

The removal of syringes in accordance with each of the above-noted ramretraction protocols 184 a-d of FIGS. 7-10 may be entirely automated inany appropriate manner, or stated another way the actual syringe removaloperation(s) could be part of a programmed sequence. Another option isto exclude from any programmed sequence utilized by any of the ramretraction protocols 184 a-d, each step directed to removingsyringes—the actual removal of each syringe would not be part of aprogrammed sequence in this instance. Each syringe could thereby beremoved entirely by hand or manually. At least one or more aspects, thatat least somehow relate to the removal of each syringe discussed abovein relation to the ram retraction protocols 184 a-d, may be included aspart of a programmed sequence (e.g., issuing a prompt or the like on agraphical user interface that it is now okay to manually remove thesyringes; monitoring the ‘installed’ status of the syringes—indicatingwhether or not a syringe is still installed on the powerhead).

The foregoing description of the present invention has been presentedfor purposes of illustration and description. Furthermore, thedescription is not intended to limit the invention to the form disclosedherein. Consequently, variations and modifications commensurate with theabove teachings, and skill and knowledge of the relevant art, are withinthe scope of the present invention. The embodiments describedhereinabove are further intended to explain best modes known ofpracticing the invention and to enable others skilled in the art toutilize the invention in such, or other embodiments and with variousmodifications required by the particular application(s) or use(s) of thepresent invention. It is intended that the appended claims be construedto include alternative embodiments to the extent permitted by the priorart.

What is claimed:
 1. A method of operation for a medical fluid deliverysystem comprising a power injector, that in turn comprises a powerhead,first and second syringes, and first and second syringe plunger drivers,the method comprising the steps of: executing a programmed retractionsequence, comprising the steps of: executing a first retracting stepcomprising retracting said first syringe plunger driver toward a firstfully retracted position, wherein said first retracting step furthercomprises retracting said first syringe plunger driver to a firstintermediate position that is reached before said first fully retractedposition during retraction of said first syringe plunger driver, whereinsaid first syringe plunger driver is stopped at said first intermediateposition; executing a second retracting step comprising retracting saidsecond syringe plunger driver toward a second fully retracted position;and executing a third retracting step comprising retracting said firstsyringe plunger driver from said first intermediate position to saidfirst fully retracted position; removing said first syringe from saidpowerhead after at least part of said first retracting step has beenexecuted; and removing said second syringe from said powerhead after atleast part of said second retracting step has been executed.
 2. Themethod of claim 1, wherein retracting said first syringe plunger driverto said first intermediate position for said first retracting stepcomprises moving said first syringe plunger driver a distancecorresponding with a fluid volume of no more than about 5 milliliters.3. The method of claim 1, wherein retracting said first syringe plungerdriver to said first intermediate position for said first retractingstep comprises relieving pressure from said first syringe.
 4. The methodof claim 1, wherein said second retracting step is initiated after saidfirst syringe plunger driver has reached said first intermediateposition from said first retracting step.
 5. The method of claim 1,wherein retracting said first syringe plunger driver to said firstintermediate position for said first retracting step and at least partof said second retracting step are simultaneously executed,
 6. Themethod of claim 1, wherein said second retracting step comprisesretracting said second syringe plunger driver to a second intermediateposition, and wherein said second syringe plunger driver is stopped atsaid second intermediate position.
 7. The method of claim 6, whereinsaid removing said second syringe step is executed after said secondsyringe plunger driver has reached and been stopped at said secondintermediate position.
 8. The method of claim 6, further comprising thestep of executing a fourth retracting step comprising retracting saidsecond syringe plunger driver from said second intermediate position tosaid second fully retracted position.
 9. The method of claim 6, whereinretracting said second syringe plunger driver to said secondintermediate position for said second retracting step comprises movingsaid second syringe plunger driver a distance corresponding with a fluidvolume of no more than about 5 milliliters.
 10. The method of claim 6,wherein said second retracting step is initiated after said firstsyringe plunger driver has reached said first intermediate position fromsaid first retracting step.
 11. The method of claim 6, wherein saidfirst and second syringe plunger drivers are simultaneously retracted tosaid first and second intermediate positions, respectively, by saidfirst and second retracting steps, respectively.
 12. The method of claim1, wherein said second retracting step comprising retracting said secondsyringe plunger driver to said second fully retracted position withoutstopping.
 13. The method of claim 1, wherein said programmed retractionsequence is initiated by software.
 14. The method of claim 1, whereinsaid programmed retraction sequence is initiated by user input.
 15. Themethod of claim 1, further comprising the step of executing a fluiddelivery protocol, wherein said programmed retraction sequence isinitiated after a completion of said fluid delivery protocol.
 16. Themethod of claim 1, further comprising the steps of: extending said firstsyringe plunger driver; delivering a first fluid from said first syringein response to said extending said first syringe plunger driver step;extending said second syringe plunger driver; and delivering a secondfluid from said second syringe in response to said extending said secondsyringe plunger driver step, wherein said first retracting step isinitiated after an execution of said delivering a first fluid step, andwherein said second retracting step is initiated after an execution ofsaid delivering a second fluid step.
 17. A method of operation for amedical fluid delivery system comprising a power injector, that in turncomprises a powerhead, first and second syringes, and first and secondsyringe plunger drivers, the method comprising the steps of: executing aprogrammed retraction sequence, wherein said programmed retractionsequence is automatically initiated by a programmed input to said powerinjector, and wherein said executing a programmed retraction sequencestep comprises the steps of: executing a first retracting stepcomprising retracting said first syringe plunger driver toward a firstfully retracted position; and executing a second retracting stepcomprising retracting said second syringe plunger driver toward a secondfully retracted position, wherein said first and second retracting stepsare simultaneously executed; removing said first syringe from saidpowerhead after at least part of said first retracting step has beenexecuted; and removing said second syringe from said powerhead after atleast part of said second retracting step has been executed.
 18. Themethod of claim 17, further comprising the step of executing a fluiddelivery protocol, wherein said programmed retraction sequence isinitiated after a completion of said fluid delivery protocol.
 19. Themethod of claim 17, further comprising the steps of: extending saidfirst syringe plunger driver; delivering a first fluid from said firstsyringe in response to said extending said first syringe plunger driverstep; extending said second syringe plunger driver; and delivering asecond fluid from said second syringe in response to said extending saidsecond syringe plunger driver step, wherein said first retracting stepis initiated after an execution of said delivering a first fluid step,and wherein said second retracting step is initiated after an executionof said delivering a second fluid step.
 20. A method of operation for amedical fluid delivery system comprising a power injector, the methodcomprising the steps of: providing a first option to enable automaticinitiation of a syringe plunger driver retraction protocol; providing asecond option to enable manual initiation of said syringe plunger driverretraction protocol; selecting one of said first and second options;executing an injection protocol using said power injector; executingsaid syringe plunger driver retraction protocol in accordance with saidselecting step and after said injection protocol has been executed; andremoving a first syringe from said power injector after at least part ofsaid syringe plunger driver retraction protocol step has been executed.21. The method of claim 20, wherein said power injector comprises firstand second syringe plunger drivers, wherein said first syringe isassociated with said first syringe plunger driver, and wherein a secondsyringe is associated with said second syringe plunger driver, saidmethod further comprising the steps of: executing a programmedretraction sequence that is automatically initiated by a programmedinput to said power injector, wherein said programmed retractionsequence comprises the steps of: executing a first retracting stepcomprising retracting said first syringe plunger driver toward a firstfully retracted position; and executing a second retracting stepcomprising retracting said second syringe plunger driver toward a secondfully retracted position, wherein said first and second retracting stepsare simultaneously executed; removing said first syringe from saidpowerhead after at least part of said first retracting step has beenexecuted; and removing said second syringe from said powerhead after atleast part of said second retracting step has been executed.
 22. Themethod of claim 21, wherein said first retracting step comprisesretracting said first syringe plunger driver to said first fullyretracted position without stopping, and wherein said second retractingstep comprises retracting said second syringe plunger driver to saidsecond fully retracted position without stopping.
 23. The method ofclaim 20, wherein said first and second options are presented on atleast one graphical user interface.
 24. The method of claim 20, whereinsaid power injector comprises a powerhead, a second syringe, and firstand second syringe plunger drivers associated with said first and secondsyringes, respectively, wherein said method further comprises the stepsof: executing a programmed retraction sequence, comprising the steps of:executing a first retracting step comprising retracting said firstsyringe plunger driver toward a first fully retracted position, whereinsaid first retracting step further comprises retracting said firstsyringe plunger driver to a first intermediate position that is reachedbefore said first fully retracted position during retraction of saidfirst syringe plunger driver, wherein said first syringe plunger driveris stopped at said first intermediate position; executing a secondretracting step comprising retracting said second syringe plunger drivertoward a second fully retracted position; and executing a thirdretracting step comprising retracting said first syringe plunger driverfrom said first intermediate position to said first fully retractedposition; removing said first syringe from said powerhead after at leastpart of said first retracting step has been executed; and removing saidsecond syringe from said powerhead after at least part of said secondretracting step has been executed.